Since the progresses in the electric and electronic technologies, more and more products are developed for improving the human life and are used widely.
The developments of computers and calculators have induced a large variation to the human life. Not only many works can be performed rapidly, but also the data storage, input, output and others can be executed through a computer so that the working time is reduced greatly. Further, in the multi-media, by the playing through an optic disk drive, a preferred audio and video effects are present to the audiences.
In the electronic technology, audio and video signals are digitally stored in a compact disk for many years. However, in the processing technology, there are many defects necessary to be improved. There are many different compact disks having different storing formats. In the current popular digital versatile disk (DVD), many data storage formats are used, including a single layer single surface format, a single layer double surface format, a double layer single surface format, a double layer double surfaces format, etc. In the data storage, large amount of data and signals can be stored through digitally signal processing.
Referring to FIG. 1, a data section 2 in a general compact disk 1 is disclosed. In FIG. 1, a minor data storing section 200 is made on the data section 2 of the compact disk 1. This data storing section 200 is stored with data of various formats.
There are various modes in the compact disks for storing data. In the reading of data, in order to increase the reading speed, the rotary speed of the compact disk is increased mechanically. However, this mechanic way for speeding the reading of data is limited. For the current designed compact disks, since a high rotation speed will induce a large sound due to interaction with air, and moreover, the stability of the reading data is deteriorated so that faults occur in reading data. Therefore, to increase the rotary speed of an optic disk drive for speeding the reading of a data cannot solve all rotated.
Besides, in the prior art, the compact disk is rotated with a constant angular velocity (CAV). While as the data of a compact disk is read, the optic pick-up head is moved with constant linear velocity (CLV) for reading data on outer tracks of a compact disk. Further data on inner tracks is also read in CAV mode. But in reading data on inner tracks, since the frequency of a phase lock loop (PLL) is limited, when the optic pick-up head moves from outer track into inner track, the frequency is increased. If the CAV mode is converted into a CLV mode in an improper timing, it is possible that the phase lock loop cannot be operated normally. Therefore, in determining the switching timing of the CAV and CLV, the position of the optic pick-up head must be decided precisely for preventing fault.